In a camera mounted on a smartphone, etc. or an in-vehicle camera requiring 360° sensing, it is necessary to reduce a thickness. There has been a proposed device that performs imaging by analyzing an optical image penetrating a diffraction grating substrate without using a lens.
For example, Patent Document 1 describes a method of obtaining an image of an outer object by attaching a specific diffraction grating substrate to an image sensor and obtaining an incidence angle of incident light from a projection pattern generated on a sensor by light penetrating the diffraction grating substrate using inverse problem calculation without using a lens.
In addition, Patent Document 2 describes that a concentric circular grating pattern whose pitch becomes finer from a center toward an outside is used as a diffraction grating substrate.